The (in)stability of the homogenous solution \(\mathbf {s}(t)\)  can be checked by looking at the eigenvalue of the linear system (REF ), and more specifically the eigenvalue with the largest real part. In a general framework, where i.e. \(\mathbf {s}(t)\)  depends on time, we are dealing with a time dependent eigenvalue problem that can be tackled by using the Master Stability Function [1]}, [2]}. For simplicity we will hereby solely consider the case of a stationary reference orbit, i.e. \(\mathbf {s}(t)=\mathbf {s}_0\) . In this way Eq. (REF ) can be directly solved by using spectral methods. We invite the interested reader to refer to [3]} where the general case of
a periodic or even a chaotic \(\mathbf {s}(t)\)  has been analysed.
